Fiber optic cables include optical fibers which transmit information in cable television, computer, power, and telephone systems. Typically, fiber optic cables include a plurality of optical fibers housed within one or more protective layers. The number of fibers included in the cable, and the materials and thicknesses thereof used to form the protective layers, are selected based on the type of application or installation of the cable.
One specialized cable application is a “pavement crossing,” in which a cable is laid across an existing section of pavement, asphalt, or the like. Conventionally, a slot of about 10 mm is formed in the pavement section. Fiber optic cable is placed in the slot, a bedding material (such as Neoprene rubber) is placed over the cable, and the slot is then patched with pavement. Cables employed in this environment are subjected to potentially heavy mechanical loads, moisture, and heat. In addition, typically it is desirable that the cable be relatively easy to manipulate and to “connectorize” (i e., that it be receptive to connectors added in the field for connecting and splicing with other cables). Also, with many cables flexibility facilitates handling and installation of the cable, but the cable should not buckle when bent, as buckling can negatively impact the optical and mechanical properties of the cable.
Typical fiber optic cables employed in pavement crossings include a smooth metal tube (with a typical thickness of 0.020 inches) that protects fibers residing in the lumen of the tube from exterior elements. The metal tube is then covered with a polymeric jacket (polyethylene is an exemplary jacket material). The metal tube, typically stainless steel or copper, tends to provide adequate protection and is relatively easy to weld (thereby facilitating volume production. However, the relatively thick metal tube can also render the cable difficult to bend. Exemplary pavement crossing products include “MSC Road Cable,” available from Corning Cable Systems, Hickory, N.C., and similar products available from Pirelli S.p.A, Milan, Italy.
In view of the foregoing, it would be desirable for a pavement crossing cable to have adequate mechanical, optical, protective and connectorizing properties while being easier to bend during handling.